This invention relates to rotary sprinklers and, more specifically, to a rotary sprinkler having a stream interrupter or “hesitator” mechanism that operates in a controlled but non-repeating manner to achieve greater uniformity in the sprinkling pattern and/or to create unique and otherwise difficult-to-achieve pattern shapes.
Stream interrupters or stream diffusers per se are utilized for a variety of reasons, and representative examples may be found in U.S. Pat. Nos. 5,192,024; 4,836,450; 4,836,449; 4,375,513; and 3,727,842.
One reason for providing stream interrupters or diffusers is to enhance the uniformity of the sprinkling pattern. When irrigating large areas, the various sprinklers are spaced as far apart as possible in order to minimize system costs. To achieve an even distribution of water at wide sprinkler spacings requires sprinklers that simultaneously throw the water a long distance and produce a pattern that “stacks up” evenly when overlapped with adjacent sprinkler patterns. These requirements are achieved to some degree with a single concentrated stream of water emitted at a relatively high trajectory angle (approximately 24° from horizontal), but streams of this type produce a nonuniform “donut pattern”. Interrupting a single concentrated stream, by fanning some of it vertically downward, produces a more even pattern but also reduces the radius of throw.
Proposed solutions to the above problem may be found in commonly owned U.S. Pat. Nos. 5,372,307 and 5,671,886. The solutions disclosed in these patents involve intermittently interrupting the stream as it leaves a water distribution plate so that at times, the stream is undisturbed for maximum radius of throw, while at other times, it is fanned to even out the pattern but at a reduced radius of throw. In both of the above-identified commonly owned patents, the rotational speed of the water distribution plate is slowed by a viscous fluid brake to achieve both maximum throw and maximum stream integrity. Commonly owned pending application Ser. No. 12/149,262 describes additional solutions based on the ability to create fast and slow-speed intervals of rotation for the rotating stream distributor plate.